Many types of traditional connectors and sockets are populated with contact members produced by traditional metal stamping techniques. These contacts can be in a flat or “blank” format, or they can be produced with a series of forms, bends, and features to accommodate a desired function such as retention within the plastic housing. Typically, the contact members are designed based upon the needs of the application. In some cases, long life after many actuations is most important, and in some applications cost is far more important than longevity.
These contacts are typically made from a selection of Copper based alloys. Since copper oxidizes the contacts are typically plated with nickel to prevent migration, and a final coating of either a precious metal like gold or a solder-able metal such as tin. In very cost sensitive applications, the contacts are selectively plated only at the interface points where the connection will be made. While conventional contact members have served well over the years, there are some areas that could potentially be improved.
The copper based alloys used for many contacts are a compromise in material properties, where the spring constants are less than stainless steel for example, while the conductivity is less than pure copper or silver. The copper base oxidizes readily, so plating must be applied to at least a portion of the contact to improve the corrosion resistance. Often there are retention features that add electrical parasitic effects, and the demands of pitch reduction often reduce the available area for spring members. The cost of the contact members as a component is often directly related to the material content, the speed at which the contacts are stamped, and the amount and type of plating.
One type of contact method has been used which contains tiny particles of silver molded into a silicone matrix. When compressed, the silver particles touch each other can create electrical contact. Such metalized particle interconnect method suffers from high contact resistance due to the silicone material interfering with the conductive path.
Traditional IC interconnects have reached an electrical performance limit. Next generation IC devices will operate above 5 GHz and beyond and the existing IC interconnects do not provide acceptable performance levels without significant revision.